Variable pitch propeller assembly for multi-power plant aircraft



May 30, 1961 R. C. BODEM ET AL VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Filed March 19, 1956 10 Sheets-Sheet 1 MMU Their Attorney May 30, 1961 R. c. BODEM ET AL VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT l0 Sheets-Sheet 2 Filed March 19, 1956 INVENTORS. Ray C. Bode/n Roy H. Branaes Richard A. H/rsch Edward H. McDonald Carl E Wood The/r A fforney y 1961 R. c. BODEM ET AL 2,936,220

VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Filed March 19, 1956 10 Sheets-Sheet 3 //V VE/V TORS. Roy 0. Bodem Roy H. Brono'es Ric/l am A. Hirsch E dward l-l. McDonald Carl E Wood MKMQ 7' heir Attorney May 30, 1961 R. c. BODEM ETAL 2,986,220

. VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Filed March 19, 1956 10 Sheets-SheetA IN VENTORS.

Roy 6. Bo aem Roy h. Brandes R/chard A. Hirsch Edward H. McDonald Carl F? Wood The/r Attorney May 30, 1961 R. c. BODEM ET AL VARIABLE PITCH FROPEILLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT l0 SheetsSheet 5 Filed March 19, 1956 IN VENTORS. Roy 6. Bo o'em Roy H. Brande:

Richard A. Hirsch Edward H. McDonald By Carl E Wood The/r A Horney May 30, 1961 R. c. BODEM ETAL 2,986,220

VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Flled March 19, 1956 10 Sheets-Sheetfi BETA FOLLOW UP POWER LEVER Posmmv lo [:uo TRANSITION RANGE BETA muss Roy 6. Boa'em Roy H. Bram/es Richard A. Hirsch Edward H. McDonald Carl E W0 00 The/r Attorney May 30, 1961 R. c. BODEM ETAL 2,986,220

VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Filed March 19,' 1956 10 Sheets-Sheet 7 /A/ VIEW T 0R5. Roy 6. Bo a'em Roy H Bra/Ides Ric/2 ard A. Hirsch Edward H. McDonald Carl E Wood 6 M Mi a The/r Attorney May 30, 1961 R. c. BODEM EI'AL VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT 10 Sheets-Sheet 8 Filed March 19, 1956 Roy h. Bra/Ides Richard A. Hirsch Edward H. Mc Donald Carl E Wood The/r Attorney May 30, 1961 R. c. BODEM ETAL 2,986,220

VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Filed March 19, 1956 10 Sheets-Shame INVENTORS.

Roy 6. Bodem L70 I I ifioyh'. Brandes 363 Richard A. Hirsch 15 EdwardhfMcDona/d (3c? BY Carl E Wood Tl. -ir Attorney May 30, 1961 R. c. BODEM ET AL 2,986,220

VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Filed March 19, 1956 10 Sheets-Sheet 10 TOPEES-SUEE- CONDU/T-193 T0 CONDU/TZZ 2 l n F T0 DEA/N GOA/27017243 TO CONDU/ T 323 TO CONDU/T .281

I NVENTORS Roy 6'. Bode m Roy H Bra ndes Ric/1 ard/I. H1 rscb Edward H. McDo maid BY Carl If Wood The/r- Altar-he y United States Patent (3 VARIABLE PITCH PROPELLER ASSEMBLY FOR MULTI-POWER PLANT AIRCRAFT Roy C. Bodem and Roy H. Brandes, Dayton, Richard A. Hirsch, West Milton, Edward H. McDonald, Tipp City, and Carl F. Wood, Dayton, Ohio, assignors to General Motors Corporation, Detroit, Mrch., a corporation of Delaware Filed Mar. 19, 1956, Ser. No. 572,348

5 Claims. (Cl. 170- 135.)

T his invention pertains to variable pitch propellers, and particularly to a variable pitch propeller assembly designed for use with gas turbine powered aircraft.

One of the essential requirements of presently available commercial gas turbine propeller plants is that of substantially constant speed operation. Thus, a variable pitch propeller assembly driven by a turbine must include 'an isochronous governor of high sensitivity for controlling propeller pitch to maintain turbine speed substantially constant during normal flight operation. Preferably, the propeller assembly includes hydraulically actuated motor means for varying propeller pitch and during constant speed operation, propeller pitch is controlled by a hydraulic governor. The hydraulic governor is calibrated to maintain a selected speed of propeller rotation, and, hence, a selected speed of turbine rotation, and the speed setting of the governor cannot be manually adjusted by the pilot during normal aircraft flight operation. However, in a multi-power plant aircraft, it is necessary to have the several turbine-propeller combinations operate at a synchronous speed, and to accomplish this result, mechanism can be incorporated for synchronizing the speed of slave turbine propeller combinations with a master turbine propeller combination. The speed synchronizing mechanism, per se, forms no part of this invention, but may be of the general type wherein the speed synchronizing mechanism can automatically adjust the hydraulic governors of the sleeve turbine propeller combinations which deviate from the speed of the master combination within a limited range by electromotive means. In addition, it is desirable to phase synchronize the propellers to maintain a predetermined phase relationship between the master propeller and the slave propellers. The phase synchronizing mechanism, per se, likewise, constitutes no part of this invention but may comprise an electrical unit for actuating solenoid valves connected in parallel with the hydraulic governors of the slave" propellers.

Moreover, the propeller assemblies of a multi-turbine powered aircraft preferably include safety feathering means for increasing the pitch of a propeller driven by a failing turbine during normal propeller operation. The safety feathering means are of the uncommitted type wherein the pitch position of the propeller driven by a failing turbine is increased to reduce the drag on the aircraft, but which does not automatically completely feather the propeller so that in the event that the failing turbine should recover, control of propeller pitch will be automatically returned to the hydraulic governor, thereby enabling this propeller-turbine combination to again assist in propelling the aircraft. The failure of a power plant may be detected by sensing negative propeller shaft torque. It is also advantageous to incorporate automatic cornmitted" feathering means in the propeller assemblies for a multi-power plant aircraft, which feathen'ng means are only operative during take-01f of the air-' craft when the power lever is in the take-off position, and, in addition, are automatically disarmed upon a failure of one power plant. Thus, during take-off, the propeller of a failing power plant is automatically moved to the feathered position so as to reduce the drag of the inoperative power plant to a mini-mum during take-01f The failure of a power plant during take-off may be detected by sensing negative propeller shaft thrust. In addition, each propeller assembly for a plural power plant aircraft should include emergency feathering means and normal feathering means.

Since a variable pitch propeller can be adjusted to develop positive thrust, negative thrust and also be ad justed to a pitch position wherein it imposes a minimum' load on the power plant, i.e. a substantially flat pitch, or start angle, where a minimum thrust is developed, it is desirable to include means for manually selecting blade angles, or pitch positions, as well as means for adjusting the propeller blades to the full reverse position. These advantages of a variable pitch propeller increase the maneuverability and flexibility of ground operation of an aircraft. However, in order to realize the full benefits of a variable pitch propeller which includes safety feathering means actuated by a negative propeller shaft torque sensing device, means must be incorporated in the propeller assembly for disabling,'or blocking out, the safety feathering means during propeller operation in the regime of manually selected blade angles. The disabling means for the safety feathering means must be incorporated since when the aircraft is making the approach for a landing with the propeller blades at the mini mum flight low pitch position, under some conditions negative propeller shaft torque will be developed when the propeller blades are moved from this low positive pitch position through flat pitch and into the negative thrust range. Hence, if disabling means for the safety feathering means were not incorporated, the pilot would be unable to manually select a blade angle in the negative thrust range.

In order to facilitate maintenance and repair of a variable pitch propeller assembly, it is desirable to design the propeller so that the major valve components of the hydraulic control system are readily accessible without removing the entire propeller assembly from the propeller shaft. Moreover, it is extremely desirable to group the valve components into separate assemblies according to function and importance, for instance, a constant speed assembly, a feathering assembly, a pitch stop and pitch lock assembly and a solenoid valve assembly. In the instant propeller assembly, the major valve assemblies are accessible through removable plates in the regu-' lator assembly.

Inasmuch as it is well recognized that the failure of a turbine during take-off of a multi-power plant aircraft may result in a mishap, the multi-power plant aircraft includes automatic feathering means, as aforementioned, However, the automatic feathering means may not detect an incipient turbine failure, so that it is desirable to manually schedule a propeller pitch position only slightly below the pitch position required for normal governing during take-off so as to reduce the drag created by a failingengine. In other words, it is highly advantageous to schedule a blade angle above the flight idle ang1e, or" low pitch stop position, during take-off since if the pitch' angle is higher during take-off, the failure of a turbine will not result in the magnitude of drag that would occur if the blades were at the lot pitch stopposition.

addition, the beta follow-up system will always reduce, and usually prevent propeller overspeeding during takeoff which might be caused by a governor malfunction. However, as soon as the take-off operation is completed and the power lever is moved to an intermediate position in the cruise range, it is desirable to reduce the minimum flight low pitch stop position to the minimum safe flow flight angle. The present invention relates to a variable pitch propeller assembly including all of the desirable features hereinbefore alluded to.

Accordingly, among our objects are the provision of a variable pitch propeller assembly including means for scheduling a minimum blade angle during take-otf, which is higher than the minimum safe low flight angle; the further provision of propeller assembly including hydraulic means for adjusting the pitch thereof and a manually variable hydraulic low pitch stop therefor; the further provision of a variable pitch propeller assembly including safety feathering means and means for disabling the safety feathering means during propeller operation in the manually selected blade angle range; the further provision of a variable pitch propeller having fluid pressure operated means for varying propeller pitch and a self-contained fluid reservoir rotatable with the propeller and containing valve means for controlling the pitch changing means; the further provision of a variable pitch propeller assembly of the aforesaid type including an independent selfcontained fluid reservoir and pump means for feathering the propeller; and the further provision of propeller assembly of the aforesaid type including a rotatable reservoir assembly having removable means permitting access to the major valve assemblies carried by the reservoir structure; the further provision of a propeller assembly of the aforesaid type including nonrotatable control means which extend into the rotatable reservoir structure for controlling operation of valve assemblies contained therein; and the further provision of an emergency feathering system for a variable pitch propeller including two independent control elements for etfecting propeller feathering independently of each other under emergency conditions; and the still further provision of a method of operating a propulsion system for an aircraft having a turbine driven variable pitch propeller whereby the minimum scheduled blade angle is increased during power lever movement between flight idle and take-off positions.

The aforementioned and other objects are accomplished in the present invention by designing the propeller assembly so that all of the manually adjustable primary control valves are actuated mechanically through linkages from a stationary adapter assembly. Specifically, the propeller assembly includes a hub, which is adapted for connection to the propeller shaft of a turbine. The hub is formed with a plurality of radially extending sockets within which propeller blades are journaled for rotation about their longitudinal axes throughout a range of pitch positions from full reverse to a feathered position. The propeller assembly is generally similar to that disclosed in copending applications Serial No. 485,921, Ditmer, et al., now patent No. 2,891,627, and Serial No. 485,922, Brandes, et al., now Patent No. 2,919,752, both filed February 3, 1955, and assigned to the assignee of this invention.

Accordingly, the pitch position of each propeller blade is controlled by a fluid pressure actuated torque unit assembled into each hub socket and enclosed by the hollow root portion of its respective propeller blade. Each torque unit includes a cylinder which rotates upon reciprocable movement of a piston disposed therein, each cylinder being connected to its respective blade through an indexing ring. The pitch positions of the several propeller blades in the hub are coordinated by a master gear which meshes with gear segments formed on the torque unit cylinders, the master gear being journaled in the hub for rotation about the horizontal propeller axis.

A rotating reservoir assembly, or regulator, is attached to the rear of the propeller hub. The regulator assembly contains a quantity of oil for the self-contained hydraulic system and includes a housing, a cover, a slip ring assembly, valve assemblies which rotate with the propeller about a stationary adapter assembly and accessory plate. A plurality of pumps are mounted on the regulator housing, these pumps being energized incident to propeller rotation about the stationary adapter assembly which includes a pump power gear. All of the control valve assemblies are mounted on the regulator housing, and the hydraulic connections between the valve assemblies and the torque units are formed by tubes and passages formed as an integral part of the regulator housing and the propeller hub. In addition, the major control valves are integrated into unitary valve assemblies which are removable through access openings in the regulator cover. The access openings are closed by plates removably attached to the regulator cover.

The statonary adapter assembly includes, in addition to the pump power gear, a synchronizing lever, a feathering lever, and a control lever. Each lever is connected to a ring gear which elfects rotation of a plurality of pinion gears attached to high lead screws. The high lead screws, rotated by each of the three levers, threadedly engage separate axially movable rings disposed within the regulater and slidable on an adapter sleeve, i.e. a control ring, a feathering ring and a speed ring. The control ring of the adapter assembly is operatively connected with the governor valve assembly, as well as the feathering valve assembly. The feathering ring is operatively connected to the feathering valve assembly and the speed ring is connected to the speed adjusting means of the governor valve assembly.

A feathering pump and reservoir assembly is attached to the front of the propeller hub and contains an electric motor, a pump drivingly connected to the motor, an oil filler attachment, a feathering pump control valve assembly and a separate reservoir of oil independent of the regulator reservoir. The feathering pump reservoir is air cooled and contains sufiicient oil for completely feathering the propeller at all times.

In addition, the propeller assembly includes a mechanical low pitch stop assembly and a mechanical pitch lock assembly, which may be of the type disclosed in copend' ing applications Serial No. 545,033, now abandoned and Serial No. 545,034 Flaugh, et al., both filed on November 4, 1955, and assigned to the assignee of this invention.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

Fig. 1 is a view, partly in section and partly in elevation, of a propeller assembly constructed according to this invention with certain parts removed.

Fig. 2 is a fragmentary enlarged view, partly in section and partly in elevation, taken generally along line 22 of Fig. l.

Fig. 3 is an isometric view of the regulator assembly with certain parts removed.

Fig. 4 is an enlarged fragmentary view, partly in section and partly in elevation, of a portion of the regulator assembly with the governor assembly access plate removed.

Fig. 5 is an isometric view, partly in section and partly in elevation, of the regulator assembly including the stationary adapter assembly and accessory plate.

Fig. 6 is an isometric view of the regulator housing with the valve assemblies and pumps mounted thereon.

Fig. 7 is an isometric view, partly in section and partly in elevation, of the feathering pump. and reservoir assembly.

Fig. 8 is a schematic view of a turbine-propeller combination illustrating the propeller control system.

Fig. 9 is a view, partly schematic and partly structural, of the propeller hydraulic control system, together with the blade torque unit, hub, and regulator assembly.

Fig. 10 is a view, in elevation, of the control ring gear assembly of the regulator assembly.

Fig. 11 is a fragmentary sectional view taken along line 11-11 of Fig. 10.

Fig. 12 is a graph depicting blade angles that can be manually scheduled by movement of the power lever.

Figs. 13 through 16 are diagrammatic views illustrating operation of the feathering control valve.

Figure 17 is an enlarged sectional view of the pitch stop and pitch lock valve assembly shown in Figure 9.

With particular reference to Fig. 1, a propeller assembly is shown including a hub 20 having a plurality of radially extending sockets 21 within which propeller blades 22 are journaled for rotation about their longitudinal axes throughout a range of pitch positions from full reverse to full feather. Each propeller blade 22 encloses its own torque unit 23, as shown in Fig. 9, which is assembled into its respective hub socket, the torque units being'of the general type disclosed in aforementioned copending application Serial No. 485,921 new Patent No. 2,891,627. The hub is formed with a manifold, or passage means, for conveying hydraulic fluid under pressure from a regulator assembly 24 to opposite sides of the torque units mounted in the hub sockets so as to move the blades 22 in either an increase pitch direction or a decrease pitch direction.

With reference to Figs. 1 and 5, the regulator assembly includes a housing 25 attached to the rear of the propeller hub so as to rotate therewith, a cover 26 attached to the housing 25 having slip rings 27 thereon, a stationary adapter assembly 28, a portion of which is enclosed by the cover 26 and a stationary accessory plate 29, which is connected to the adapter assembly. Bearing means are incorported for journaling the regulator housing and cover about the stationary adapter assembly, and the housing, cover and stationary adapter assembly form a doughnut shaped reservoir structure containing hydraulic fluid. In order to prevent the leakage of hydraulic fluid from the reservoir structure, suitable sealing means are disposed between the adapter assembly and the rotatable components of the regulator assembly.

As seen in Fig. 6, a plurality of control components are mounted on the rotatable regulator housing 25, the control components including pumps and valves. As seen in Fig. 6, the regulator valve components are grouped into four major assemblies comprising a constant speed, or governor valve, assembly 30, a featheringvalve assembly 31, a solenoid valve assembly 32, and a pitch stop and pitch lock valve assembly 33. A jitter valve assembly 34 and a centrifugal breather valve assembly 35 are mounted on the housing 25. The breather valve assembly 35 is of the type shown in the Haines Patent 2,357,400, and constitutes no part of this invention, this valve assembly being operable to vent the reservoir structure to atmosphere to prevent the build-up of air pressure therein, and has no connection with the propeller hydraulic control system. Four gear type pumps 36 are mounted on the rotatable housing 25, each pump having a driving gear 37, which meshes with a stationary pump power gear 38, that forms a component of the stationary adapter assembly, as seen in Fig. 5. Thus, upon rotation of the regulator housing 25, the pumps 36 are energized due to relative rotation between the housing 25 and the stationary pump power gear so as to draw hydraulic fluid from the reservoir and discharge fluid under pressure into conduit means formed as an integral part of the housing 25 As seen in Fig. 3, the regulator cover 26 is formed with four access openings, which are located substantially 90 apart. It is also to be noted that the four major valve assemblies 30, 31, 32 and 33 are mounted on the regulator housing 25 substantially 90 apart so as to be located directly beneath the access openings in the regulator cover. 26. As seen in Fig. 3, the access openings in the regulatorcover 26 are normally closed by access plates 39, 40, 41

In addition, as seen in Fig. 3, the access plate 39 for the governor valve assembly 30 has a threaded hole 44 therein adapted to receive a threaded plug 45. By this arrangement, only the plug 45 need be removed from the plate 39 to insert a screwdriver for rotating a member to manually adjust the load on the governor spring to calibrate the governor to the selected speed setting. The governor spring assembly for the governor valve assembly and the manual adjusting means therefor may be of the type disclosed in the aforementioned co-pending application, Serial No. 485,922, now Patent No. 2,919,752. The plate 39 also includes a transparent insert 46 by which means the oil level in the regulator can be visually checked when the propeller is stationary and the regulator is at a predetermined angular position.

The manner in which the major valve assemblies 30' through 33 are attached to the regulator housing 25 is clearly shown in Figs. 4 and 6. Thus, the housings, or casings of each of the major valve assemblies are formed with flanges 47, which extend substantially in radial directions on the housing 25. As seen particularly in Fig;

4, the flanges 47 are formed with spaced semi-circular notches 48 and 49. The valve assemblies are attached to the regulator housing 25 by a clamp member 50 having bolts 51 and 52 at opposite ends, the bolts extending through the grooves 48 and 49 in the flange 47 and being threaded into holes in the regulator housing 25. To re move any of the major valve assemblies 30 through 33 from the regulator assembly, it is only necessary to remove the access plate which covers the access opening in alignment with the particular valve assembly to be removed. Thereafter, the bolts 51 are withdrawn from their threaded holes in the regulator housing 25, after which, the clamp members 50 may be swung away from the flanges 47, thereby disconnecting the valveassembly from the housing 25 to permit its removal through its respective access opening. In order to maintain the valve assemblies in fixed relation relative to the housing 25 when they are assembled therewith, as shown in Fig. 4, each clamp member 50 is formed with an outwardlycurved portion 53 adapted to engage a dished portion 54 on the flange 47. The co-engaging curved surfaces 53 and 54 function to equalize the loads on the bolts 51 and 52. The valve components integrated into each major valve assembly will be described hereinafter, each valve assembly being properly located on the housing 25 by dowels, not shown.

With particular reference to Figs. 1 and 2, a feathering pump and reservoir assembly 55 is mounted on the front face of the propeller hub 20. As seen in Figs. 2 and 7,'

the feathering pump and reservoir assembly comprises a finned cover which is attached to a back plate 57, the back plate being attached to the propeller hub by any suitable means, such as bolts. An electric motor 58 is attached to the back plate 57, the axis of the motor being coincident with the horizontal propeller axis, and the electric.

motor is disposed within the axial through bore in the on the back plate 57. A check valve assembly 69, a

feathering pump pressure control valve 70 and a check valve assembly 71 are also mounted on the back plate 57, as seen in Fig. 7. The finned cover 56 is enclosed by a sheet metal shroud, or shield, 72, the shield 72 being attached to the cover 56. The shield 72 includes an outwardly extending tubular portion 73 having a threaded section 74.

As seen in Figs. 1 and 2, the propeller hub is enclosed by a one-piece spinner shell 75 having a central opening in the nose thereof, which is formed by a tube 76. This tube pilots on the tubular portion 73 of the shield 72, and the spinner is secured to the propeller by a retaining nut 77, which engages the threads 74 formed on the shield 72. The nut 77 is secured to the spinner nose tube 76 by an annular coupling assembly 78 which is attached thereto by means of a screw device 79.

The feathering pump reservoir cover 56 carries an oil filler attachment 80 in the nose portion thereof, which may be removed to fill the feathering pump reservoir and the regulator reservoir by means of a pressure filling device, not shown. Hydraulic fluid from the feathering pump reservoir, which acts as a heat exchange device for cooling the hydraulic fluid of the propeller hydraulic system, can flow from this reservoir to the regulator reservoir through a pick-up tube 81, which has an open end at the centerline of the feathering pump reservoir, and communicates with a hub passage, not shown, with the regulator reservoir. Thus, the reservoir 55 is maintained full of oil at all times. As will be pointed out more particularly hereinafter, oil in the feathering pump reservoir is forced to flow through the pick-up tube 81 by drain oil flowing from the regulator control valves and the torque units during propeller rotation. Drain oil under pressure is admitted to the feathering pump reservoir through check valve assembly 71. The feathering pump reservoir is cooled during propeller rotation and flight of the aircarft to which the propeller is attached by reason of air flow through the nose of the spinner which flows in contiguous relation to the cover 56 of the feathering pump reservoir 55. Air fiow across the reservoir 55 is aided by the air pump formed by the shield 72 and the fins 82 on the cover.

As seen in Fig. l, the aft section of the spinner shell 75 is attached to a spinner mounting ring 83, which is bolted to the regulator cover 26. The spinner mounting ring also includes four sections 84 for closing the rear portion of the spinner cutouts through which the propeller blades 22 project. In addition, the spinner assembly includes islands 85 surrounding each spinner cutout, which islands are of two-piece construction. The leading edge portion of each island is attached to the spinner shell 75 and the trailing edge portion of each island is attached to the spinner mounting ring 83. The islands 85 cooperate with cuffs 86, as seen in Fig. 8, attached to the shank portions of each propeller blade to form an airfoil surface at a particular blade angle, namely, the selected cruise angle. Cooling air for the feathering pump reservoir 55, which flows through the nose of the spinner can escape past the spinner islands around the propeller shanks.

With particular reference to Fig. 8, a typical aircraft power plant including the propeller assembly of this invention is shown in schematic form. The power plant includes a gas turbine 90, the output shaft 91 of which is connected through a gear reduction unit 92 to a propeller shaft 93 having splines 94 adapted to mate with complementary splines on the propeller hub, not shown. The regulator assembly 24 of the propeller is schematically shown in Fig. 8, as well as the stationary accessory plate 29, it being understood that the accessory plate and the stationary adapter assembly connected therewith are attached to the stationary housing of the gear reduction unit 92. The stationary adapter assembly includes a control lever 95, a feathering lever 96 and a speed lever 97. The control lever 95 is shown connected by a link 98 with a bellcrank 99 to a propeller control link 100, the opposite end of which is connected to an output arm 101 of a coordinating control 102. The coordinating control, per se, constitutes no part of this invention, and suffice it to say, that the coordinating control 102 has two input arms 103 and 104, which are connected by links 105 and 106, respectively, to an emergency feathering lever 107 and a cockpit mounted power lever 108. The coordinating control may be of the type shown in McDowall et al. Patent 2,860,712. The coordinating control 102 is also connected by links 109 and 110 to the gas turbine fuel control 111.

The power lever 108 is movable in a quadrant defined by a member 1 12. The member 112 has a pair of spaced slots 113 and 114 therein connected by a gate 115. The power lever is movable in a clockwise direction, as viewed in Fig. 8, from a full reverse position through a start position, a flight idle position, and a cruise range to a take-off position. Between the full reverse and flight idle position, the pitch position, or blade angle, of the propeller blades is manually scheduled, or selected. Accordingly, this range of power lever movement may be called the beta range, one end of the beta range constituting the full reverse position. Between flight idle and the take-off position, the pitch position of the propeller blades is primarily under governor control so as to maintain a substantially constant turbine speed, although a beta follow-up system, to be described hereinafter, is operative in a portion of the cruise range adjacent the take-off position.

The emergency lever 107, when pulled, calls for emergency feathering of the propeller blades through the control link 100, and at the same time, shuts off the fuel to the gas turbine. The emergency feathering arrangement will be described in greater detail hereinafter. Normal propeller feathering may also be effected by moving a switch 116 to call for feathering, the switch 116 completing a circuit through wire 117 to an automatic feathering solenoid 118 attached to the accessory plate and connected by a link 119 with the feathering lever 96. Movement of switch 116 to the feather or the unfeather position also energizes the electric motor driven feathering pump for a timed interval through the slip ring assembly 27. To unfeather the propeller, the switch 116 is moved to the unfeathered position. The switch 116 is spring loaded to the intermediate, or normal, position, by any suitable arrangement, not shown.

As seen in Fig. 8, an alternator 120 is driven from the reduction gear assembly 92 of the propeller assembly shown, which constitutes a slave turbine propeller combination. The frequency of the current produced by the alternator 120 is directly proportional to the speed of rotation of the propeller shaft 93, and this speed is compared with the speed signal produced by a master turbine propeller driven alternator 121 by an electromechanical speed synchronizer 122, constituting no part of this invention. The speed synchronizer 122 is connected by a wire 123 with a cockpit switch 124 having a center position, a speed synchronize position, and a phase synchronize position. In addition, the speed synchronizer 122 is connected by a wire 125 with an electrical phase synchronizer 126, likewise constituting no part of this invention. The speed synchronizer 122 is connected by a wire 127 to an electric motor 128, which is connected by a linkage 129 with the speed lever 97. The phase synchronizer 126 is connected by a plurality of wires indicated by numeral 130 to the slip ring assembly 27. Either the phase synchronizer 126 or the speed synchronizer 1'22 may be connected with the slave propeller assembly, but both cannot be connected therewith at the same time.

With particular reference to Fig. 5, the regulator assembly is shown partly in elevation and partly in section, from which it can be seen that the stationary accessory plate 29 carries brush blocks 132 which are electrically connected to the slip ring assembly 27. Each brush block assembly is electrically connected to a cannon type electric outlet plug 133, by which means electrical energy is supplied to the brush blocks and slip rings. A solenoid 134 capable of actuating an axially movable stop member 135 is supported on the accessory plate 29. The stop member 135 cooperates with a stop lug 317 formed on a ring gear 136, Fig. 10, which is connected to rotate upon movement of the control lever 95, as will be pointed out more particularly hereinafter. The solenoid stop prevents inadvertent movement of the control lever 95 and its associated control gear 136 into the beta range of propeller operation. The solenoid stop can be removed by energizing the solenoid by suitable switch means, not shown, in the aircraft cockpit. The feathering lever 96 is connected with a feathering ring gear 137. The feathering lever 96 is biased by suitable spring means, not shown, to a normal position and can be moved to call for propeller feathering either by movement of a link 138, which is connected by means of a bellcrank 139 and a link 140 to a lever 96, or by energization of the automatic feathering solenoid 118, as seen in Fig. 8. The link 138 is mechanically positioned by a negative propeller shaft torque sensing device, not shown, within the gear reduction unit 92. The automatic feathering solenoid 118 can be energized during propeller take-ofi through wire 141 from a negative propeller shaft thrust sensing device, not shown, within the gear reduction unit 92, neither sensing device constituting a part of this invention.

The speed lever 97 is connected with a ring gear 142, which is located in a plane common to that of ring gear 137. The ring gear 137, being of smaller diameter than ring gear 142, is externally toothed, while the ring gear 142 is internally toothed. The speed lever is shown connected by linkage 129 to a shaft 143 of the electric motor 128, the housing of which is attached to the accessory plate 29. As aforementioned, energization of the motor 128 is controlled by the speed synchronizer 122.

As seen in Fig. 5, the accessory plate 29 is connected by a plurality of bolts 144 to a stationary sleeve 145 of the adapter assembly 28. The stationary sleeve 145 supports bearing means 146 and 147 which journal the regulator housing and cover for rotation about the sleeve 145. In addition, the regulator housing 25 and the cover 26 carry seals 148 and 149, which engage the sleeve 145 so as to prevent the leakage of hydraulic fluid from the reservoir structure.

The pump power gear 38 is shown connected by bolts to the stationary sleeve 145. In addition, three rings are adapted for axial movement on the stationary sleeve 145, namely a feathering ring 150, a control ring 151 and a speed ring 152. The feathering ring engages three high lead screws 153 disposed 120 apart, which high lead screws are driven by pinion gears 154 that mesh with the ring gear 137. Accordingly, upon rotation of the ring gear 137 by means of the feathering lever 96, axial move ment will be imparted to the feathering ring 150.

The control ring 151 threadedly engages three high lead screws 155 spaced 120 apart, the high lead screws 155 being attached to pinion gears 156, which mesh with both the ring gear 136 and a synchronizing gear 157. As will be pointed out more particularly hereinafter, rotation is only imparted to the high lead screws 155 throughout a portion of the total movement of the control lever 95 and the ring gear 136 so as to elfect axial movement of the control ring 151.

The speed ring 152 is threadedly connected to three high lead screws 158 which are attached to pinions 159 that mesh with the internal ring gear 142 which is attached to the speed lever 97. Accordingly, upon angular movement of the speed lever 97 by the electric motor 128, axial movement will be imparted to the speed ring 152. Fig. also shows a cross-sectional view of the conduit r l0 7 means, or tube insert assembly 160 of the regulator housing 25.

With particular reference to Fig. 9, the propeller hydraulic control system will be described. As aforemen-- tioned, four major valve assemblies are mounted on the housing 25 of the regulator. The pumps 36, which are energized incident to propeller rotation, draw fluid from the regulator reservoir and discharge fluid under pressure into a conduit 167. The conduit 167 is connected through a one-way check valve 168 to a high pressure supply conduit 169 constituting part of the tube insert assembly of the regulator housing 25. The conduit 169 is connected to branch conduits 170 and 171. The conduit 170 communicates with a hub passage 172 which connects with the feathering pump reservoir 55, as will be described hereinafter. The conduit 170 communicates with a passage 173 of the feathering valve assembly 31. The feathering valve assembly 31 includes a casing having valve chambers 161, 162, 163 and 164 therein. The passage 173 communicates with valve chamber 163, in which the spool valve 165 having a plurality of spaced lands 174, 175, 176, 177 and 178, is disposed. The spool valve 165 is normally biased to the position shown by a spring 179. In this position, the passage 173 is connected by the annular groove between lands 176 and 177 with a passage 180. The passage 180 has branches communicating with one end and an intermediate portion of the valve chamber 161 within which a minimum pressure valve 166 is disposed. The minimum pressure valve 166 includes spaced lands 181 and 182 and is normally biased by means of a spring 183 to block communication be tween the passage 180 and a passage 184 when the propeller is stationary. However, when the pressure developed by the feathering pump is greater than the oppos-' ing force of the spring 183, or the propeller is rotating, the valve element 166 will move to the position shown so as to interconnect passages 180 and 184. The function of the minimum pressure valve 166 is to prevent the connection of the high pressure conduit 170 with the passage 184 until the pumps 36 produce suflicient flow under pressure to satisfy the requirements of the low pressure servo system to be described.

The conduit 171 communicates with a passage 185 of the governor assembly 30. The governor assembly 30 includes a casing 186 having five valve chambers 187, 188, 189, 190 and 191, all of which extend in substantially a radial direction from the horizontal propeller axis. A pressure reducer valve 192 is disposed within valve chamber 191 of the governor assembly. The pressure reducer valve 192 is of conventional design and is operative to maintain a substantially constant pressure of approximately 400 psi. in conduit 193 and passage 194, which communicate with the chamber 191. During propeller rotation at'the selected speed setting of the governor, the output pressure of the pumps 36 may be on the order of 3600 psi. The conduit 193 and the passage 194 supply this low pressure fluid to the lower pressure servo system to be described.

The low pressure system is employed to control a mechanical low pitch stop 195, which is set a predetermined amount, for instance, 2, below the hydraulic low pitch stop for the propeller blades. The low pressure servo system is also. used to control a mechanical pitch lock 196, which, when operative, prevents movement of the propeller blades in the decrease pitch direction while permitting movement of the propeller blades in the increase pitch direction. Both the mechanical low pitch stop and the mechanical pitch lock are operatively associated with a master gear 197, which is connected with each of the several blade gears 198 to coordinate their pitch changing movements. Thus, during pitch adjustment of the propeller blades, the master gear 197 rotates about the horizontal propeller axis, and, accordingly, has a predetermined angular position relative to the propeller hub for each pitch position, or angle, of the propeller blades,

aosaaao 1 1 The mechanical pitch stop and the mechanical pitch lock constitute no part of this invention and may be of the type shown in the aforementioned copending applications Serial Nos. 545,033, now abandoned, and 545,034.

Operation of the mechanical low pitch stop and the mechanical pitch lock are controlled by the pitch stop and pitch lock valve assembly 33, which includes a housing 199 having valve chambers 200, 201, 202 and 203 therein. The low pressure conduit 193 communicates with a passage 204 in the housing 199.

The low pressure passage 194 in the governor assembly 30 communicates with valve chamber 190 within which a minimum pressure valve 205 is disposed. When the propeller is rotating, or the pressure below the valve 205 is 400 p.s.i., passage 194 is connected with passages 206 and 207. However, when the propeller is stationary and the pressure in passage 194 is substantially below 400 p.s.i., a spring 208 moves the valve element 205 so as to block communication between the passage 194 and the passage 207. Passages 206 and 207 communicate with valve chamber 189 of the governor assembly within which a speed sensitive valve element 209 and a follow-up sleeve 210 are disposed for reciprocable movement. The sleeve 210 is biased upwardly by a spring 211 and is connected by a link 212 having an intermediate pivot with a distributor valve element 213 disposed in the valve chamber 188. The distributor valve element 213 includes spaced lands 214, 215, 216 and 216a, and a differential area piston 217. The upper surface of the differential piston 217, as viewed in the drawing, is of lesser area than the lower surface thereof, the difference in area being due to the diameter of the rod which connects the differential area piston 217 with the valve element proper. The smaller area of the differential area piston 217 is always subjected to the 400 p.s.i. servo pressure through a passage 218 that always communicates with the passage 206. The chamber associated with the larger area of the differential piston 217 is connected to a passage 219 that communicates with ports 220 of the sleeve 210.

The speed sensitive valve element 209 is formed with spaced lands 221 and 222, and the rod thereof is pivotally connected at its lower end to a speed sensitive lever 223 pivoted at 224 to the housing 186 of the governor assembly 30. The intermediate portion of the lever 223 is engaged by a governor spring 225. Since the valve chamber 189 is located in a substantially radial direction from the horizontal propeller axis, during propeller rotation, the valve element 209 will respond to the thrust of centrifugal force, which will tend to move it upwardly, as viewed in Fig. 9. The spring 225 opposes upward movement of the valve element 209, and the load of the spring 225 is initially adjusted so that at a preselected speed of propeller rotation, the opposing forces acting on the valve element 209, namely, centrifugal force and the spring force, will be in equilibrium so that the land 221 will close the ports 220. When the land 221 closes the ports 220, the valve element 209 is in the On Speed position. Upon an increase in propeller speed above the preselected speed setting, the thrust of centrifugal force will exceed the force of the spring 225 and the valve element 209 will move upwardly, thereby connecting ports 220 to drain. Conversely, upon a decrease in the propeller speed below the preselected speed setting, the force of the spring 225 will exceed that of centrifugal force to move the valve element 209 downwardly, thereby connecting ports 220 with the low pressure passage 206.

The low pressure passage 207 always communicates with a passage 226, which connects with an annular groove between lands 216 and 216a of the distributor valve element 213. In order to maintain the servo actuated distributor valve element 213 sensitive to a change in the pressure of fluid acting on the larger area of differential piston 217, the chamber of the larger area piston surface is connected by a conduit 227 with an hydraulic jitter-valve 228 comprising a piston 229 connected to a 12 follower 230, which engages an undulated surface 231 of the pump power gear 38. Thus during propeller rotation, the plunger 230- creates intermittent pressure pulses which serve to impart a slight jitter, or dither, reciprocating movement to the distributor valve element 213.

The high pressure fluid in passage 184 of the feathering valve assembly 31 communicates with a conduit 232 having branch conduits 233 and 234. The branch conduit 233 communicates with a passage 235 in the housing 186 of the governor assembly 30. The passage 235 communicates with valve chamber 188 between the lands 214 and 215 of the distributor valve element 213. In addition, the passage 235 communicates with valve chamber 187 within which a pressure control valve 236 for the high pressure system is disposed. The pressure control valve 236 includes a throttle landing 237 which. cooperates with a drain passage 238. The pressure control valve 236 is urged downwardly, as viewed in Fig. 9, by the high pressure fluid acting on the upper surface of land 237. In addition, the pressure control valve 236 is urged upwardly by a spring 239, the thrust of centrifugal force and pressure fluid from conduit 240 which communicates with the increase pitch chambers 241 of the torque units, as will be described hereinafter. The pressure control valve 236 maintains a pressure in passage 235, a predetermined potential above that demanded by the increase pitch chambers of the torque units. In other words, the pressure in passage 235 will always be equal to the pressure of fluid in conduit 240 plus the increment of pressure potential equivalent to the force of spring 239 and the thrust of centrifugal force. Any excess in pressure produced by the pump 36 over that maintained in passage 235 and conduits 233 and 234 by the pressure control valve 236 is diverted into the drain passage 238, which communicates with drain conduit 242 connected to branch conduit 243 and a hub passage 244, which communicates through a check valve 245 with the feathering pump reservoir 55. The conduit 242 and the hub passage 244 are always pressurized since the pressure output of the pumps 36 is always in excess of the pressure requirements established by the pressure control valve 236 during propeller rotation at the selected governing speed.

The distributor valve element 213 controls the supply and drain connections of high and low pressure fluid to opposite sides of the propeller torque units at all times except when the feathering valve assembly 31 is actuated. Thus, port 246 associated with the distributor valve is connected to an increase pitch conduit 247, which cornmunicates with a passage 248 of the feathering valve assembly 31. Passage 248 communicates with valve chamber 163 within which the valve element 165 is disposed. When the valve element 165 is in the position shown, the passage 248 is connected with a passage 249 through the annular groove between lands 177 and 178 of the valve 165. Passage 249 is, in turn, connected to a hub passage 250, which communicates with the. increase pitch chambers 241 of the torque units.

Port 251 associated with the distributor valve 213 is connected to a conduit 252, which communicates with hub passage 253. The hub passage 253 connects with a transfer tube 254 that extends through the torque unit piston 255 and communicates with the decrease pitch chamber 256 of its respective torque unit. The decrease pitch torque unit chambers 256 are always maintained under a predetermined low pressure, which produces a force on the piston in assisting relation to the centrifugal twisting moment forces effective on the blades 22 during propeller rotation, which combined forces tend to rotate the blades 22 about their longitudinal axes in a decrease pitch direction, as indicated by the arrow in Fig. 9. The predetermined low pressure maintained in the decrease pitch chambers 256 may be on the order of 50 p.s.i. as controlled by a decrease loader valve 257 disposed in valve chamber 164 of the feathering valve assembly 31 The decrease loader valve 257 actually comprises a spring 13 loaded check valve, one surface of which is exposed to the pressure maintained in the drain conduit 242, as communicated thereto through passage 258. When the pressure in the decrease pitch chambers 256 of the torque units is less than 50 p.s.i., which pressure is communicated to the other side of the loader valve 257 through conduit 252 and passage means 259, the decrease loader valve 257 will be actuated to interconnect passages 258 and 259, thereby supplying additional fluid under pressure from the drain conduit 242 to the decrease pitch chambers 256.

In the On Speed position of the speed sensitive valve 209, the low pressure fluid acting on the upper surface of the difierential piston 217 positions the distributor valve element 213 so that the port 246 is slightly open to the high pressure passage 235 and the port 251 is slightly open to drain. Thus, the increase pitch chambers 241 of the torque units are pressurized to exactly balance out the combined forces produced by the centrifugal twisting moments on the blades and the low pressure maintained in the decrease pitch chambers, so that the pitch position of the propeller blades will not change. However, when the speed sensitive element 209 senses an increase in propeller speed above the selected governing speed, the valve element 209 will move upwardly, thereby connecting ports 220 to drain so that the low pressure fluid acting on the upper surface of the difierential area piston 217 will move the distributor valve element 213 downwardly, thereby increasing the area of port 251 to the drain passage 238 and increasing the area of port 246 connected to the high pressure passage 235. The distributor valve repositions the sleeve 210 to close ports 220. Accordingly, the increase in pressure in the increase pitch chambers 241 coupled with the connection of the decrease pitch chambers 256 to drain, will cause the blades 22 to rotate in the increase pitch direction so as to increase the load on the turbine and reduce propeller speed to the selected governor speed setting, at which time, the speed sensitive element 209 will move downwardly causing the distributor valve to move upwardly to the On Speed position and reposition the sleeve 210 to close ports 220'.

Conversely, if propeller speed should decrease below the governor speed setting, the valve element 209 will move downwardly so as to connect ports 220 with the pressure passage 206. In this instance, the increase in pressure on the larger area of the ditferential piston 217 will move the distributor valve element 213 upwardly so as to connect port 246 to the drain passage 238 and open port 251 to low pressure. When the increase pitch chambers 241 are connected to drain, the constant pressure maintained in the decrease pitch chambers 256 plus the force of centrifugal twisting moments will cause the propeller blades 22 to rotate in the decrease pitch direction so as to again restore propeller speed to the governor speed setting. During movements of the distributor valve plunger 213, the sleeve 210 is moved in a follow-up relation relative to the speed sensitive element 209 through the link 212. In addition, in the absence of any pressure fluid on either side of the differential area piston 217, the spring 211 will move the distributor valve element 213 downwardly to interconnect port 246 with the passage 235 and connect port 251 with the drain passage 238. Since in the extreme downward position of the distributor valve 213, the decrease pitch chambers 256 are connected to drain, and the increase pitch chambers 241 are connected to pressure, the blades 22 will move towards the feathered position.

One end of the governor spring 225 is engaged by a movable abutment 260. In addition, the abutment 260 constitutes a piston responsive to pressure fluid in chamber 261 which is connected to conduit 262. In addition, the abutment 260 is engaged by one end of a lever 263 having an intermediate pivotal mountingto the housing 186. The other end of the lever 263 is pivotally connected to one end of a rod 265. The other end of the rod 265 has a cam 266 attached thereto engageable with a follower shoe 267 which is connected for movement with the speed ring 152. The axial position of the speed ring, and, hence, the load on the governor spring 225 of each slave propeller turbine combination can be adjusted by angular movement of the speed lever through ring gear 142, pinion gears 158 and high lead screws 159.

The pitch stop and pitch lock valve assembly 3 3 includes a rotary selector valve 270, a low pitch stop valve 271, a pitch lock servo valve 272 and a speed sensitive pitch lock control valve 273. The rotary selector valve 270 is connected to a crank arm 274 having a pivotal connection with a shoe 275 that engages the control ring 151. As seen in Figure 17, the rotary selector valve 270 comprises a plunger having a head portion 270a which has an annular groove through which a pin 27% extends. The pin 27% is secured to the casing 199 and prevents axial movement of the plunger while permitting rotation thereof. The plunger also includes a porting land 2700 and a sealing land 270d. The porting land 2700 has a pair of diametrically opposed and oppositely extending peripheral ports 277 and 278. Port 277 is connected through the valve bore 200 with pressure passage 204, and port 278 is connected through the valve bore 200 with a drain passage 270e. When the control ring is moved axially to the left, as viewed in Fig. 17, due to a predetermined counterclockwise movement of the control lever 95, as viewed in Fig. 9, which imparts counterclockwise rotation to the ring gear 136, pinion gears 156 and high lead screws 155, the crank arm 274 will rotate the selector valve 270 to interconnect low pressure passage 204 with passage 276 through port 277. In the position shown in Fig. 17, the selector valve connects passage 276 to drain through port 278.

Passage 278 is connected to conduit 262 and the top of valve chamber 201 within which the servo operable pitch stop control valve 271 is disposed. When low pressure fluid is supplied to conduit 262, the abutment 260 for the governor spring 225 is depressed to increase the governor speed setting a predetermined amount. At the same time, the pitch stop control valve 271 is moved against its spring 279 to interconnect passages 204 and 280 while blocking connection between passage 280 and drain conduit 243. The passage 280 is connected to a conduit 281 which communicates with the mechanical low pitch stop release chamber 282 so as to render the low pitch stop ineffective to prevent movement of the propeller blades below the mechanical low pitch stop angle.

From an inspection of Fig. 9, it can be seen that the lever 223 has a cam surface 285. In addition, the control ring 151 carries a second shoe 286 movable axailly therewith. It is specifically pointed out that all of the shoes which engage rings 150, 151 and 152 rotate about their respective rings during propeller rotation, while the axial position of the shoes is determined by the axial position of their respective rings. A lever 287 is pivoted to the shoe 286 at one end, the other end of which is pivoted to a nut 288. A roller type follower 289 is supported on the intermediate portion of the lever 287, the follower 289 being operatively associated with the cam 285 of the speed responsive lever 223. The follower 289 constitutes an override member for the speed sensitive pilot valve 209.

The nut 288 is slidably mounted in the governor assembly housing, as shown in Fig. 9, and threadedly engages a high lead screw 290 which is connected to and rotatable by propeller blade angle feedback means designated by numeral 300. The feedback means may be of the type disclosed in copending application Serial No. 289,110, filed May 21, 1952, now patent No. 2,761,519, in the name of Richard A. Hirsch, and assigned to the assignee of this invention. Thus, the feedback means are of the intermittent drive type, which only impart rotation to the high lead screw 290 in the beta range of blade angles, for example from a ---7 to a 32. More particularly,

the master gear 197 is formed with a partially toothed flange 291 which is engageable with a pinion 292. The pinion 292 is attached to the high lead screw 290 and is formed with a member 293 having a flat 294 thereon. The master gear is also formed with an upstanding flange or cam surface 295 axially spaced from the partially toothed flange 291. The untoothed portion of the flange 291 is coextensive with the cam surface 295 which prevents rotation of the high lead screw 290 when it engages the flat 294 on the member 293. In this instance, the cam surface 295 extends through a range of blade angles from +32 to the full feathered position. Thus, the high lead screw 290 will only be rotated during movement of the propeller blades between --7 and +32".

When the control ring 151 is moved axially to the left, as viewed in Fig. 9, through movement of the power lever 108 from the slot 114 into the slot 113 below the flight idle position, as viewed in Fig. 8, propeller blade angle or pitch position will be manually scheduled since this constitutes the beta range. Since the load on the governor spring 225 has been increased, thereby increasing the speed setting of the governor, due to actuation of the servo piston abutment 260 as controlled by the selector valve 270, the spring 225 will force the cam surface 285 of lever 223 into engagement with the follower 289. The axial position of the follower 289 will determine the amount of downward movement of the speed sensitive element 209. Downward movement of the speed sensitive element 209 will cause the distributor valve element 213 to move upwardly since ports 20 are connected to the pressure passage 206. Upward movement of the distributor valve element 213 will, through link 212, cause a follow-up movement of the sleeve 210 to interrupt the interconnection of passage 206 and ports 220. When the distributor valve lernent 213 moves upwardly, the increase pitch chambers 241 are connected to the drain passage 238, while the decrease pitch chambers 256 are connected to the low pressure passage 226. Accordingly, propeller blades will move in the decrease pitch direction, and since the propeller blades will be moved into the beta range, the feedback pinion 292 will engage the tooth flange 291 of the master gear so as to impart rotation to the high lead screw 290. When the blade angle position selected by movement of the power lever 108 to a predetermined position in the beta range has been elfected by the blades 22, the high lead screw 290 will have imparted movement to the nut 288 so as to reposition the folower 289 and move the speed sensitive valve element 209 upwardly to connect ports 220 to drain. Accordingly, the distributor valve element 213 will move downwardly due to pressure fluid acting on the upper surface of the differential piston area 217, thereby effecting upward movement of the follow-up sleeve 210. When the distributor valve element returns to a position wherein the lands 215 and 216 block ports 246 and 251, respectively, the application of pressure fluid to the decrease pitch chambers of the torque units will be interrupted and the follow-up sleeve 210 will again cause ports 220 to be closed by the land 221. Thus, the pilot 73H manually select any blade angle between full reverse (for instance 7) and flight idle (for instance, +20) within the beta range, as indicated by the graph in Fig. 12. It is pointed out that in this connection when the pilot moves the power lever 108 into the beta range, the solenoid stop member 135, which is engageable with the control ring gear 136, is removed to permit movement of the control ring gear 136 into the beta range.

With particular reference to Figs. 9, l and 11, it may be seen that the control ring gear 136 includes a flange 300 to which the control lever 95 may be attached. The control ring gear 136 is formed with three internally toothed sections 301, 302 and 303, which are circumferentially spaced by smooth arcuate sections 304, 305 and 306. However, the synchronizing gear 157 is toothed throughout its entire periphery. Moreover, the pinion gears 156 are toothed throughout their peripheries, although one of the pinion gears 156, as shown in Fig. 10, has attached thereto a member 307 with a flat 308 thereon. The member 307 is spaced axially relative to its particular pinion gear 156 and cooperates with a cam flange 309 attached to the control ring gear 136 and having an arcuate surface 310 of angular extent equal with the smooth section 304. The arcuate surface 310 cooperates with the flat 308 on the member 307 to prevent rotation of the pinion gear 156 and the synchronizing gear 157 throughout angular movement of the control ring gear 136 through the angular extent of the flange 309. Thus, during this predetermined angular movement of the control ring gear 136 by the lever 95, rotation will not be imparted to the pinion gears 156 and the high lead screws 155 due to the intermittent drive mechanism aforedescribed. This range corresponds to movement of the power lever 108 in the non-beta follow-up portion of the cruise range.

When the pilot lever 108 is moved into the beta range between full reverse and flight idle, the control ring gear 136 will be rotated in a counterclockwise direction, as viewed in Fig. 10, so that the pinion gear 156, associated with the cam flange 309, will drivingly engage the toothed section 302. Conversely, when the power lever 108 is moved in the beta follow-up portion of the cruise range to the take-off position, the pinion gear 156 associated with the cam flange 309 will engage the toothed section 301. Thus, when the power lever 108 is moved towards take-off from an intermediate position in the cruise range or moved between flight idle and reverse, rotation will be imparted to the pinion gears 156 and the high lead screws 155 so as to impart axial movement to the control ring 151. However, during power lever movement within the non-beta follow-up portion of the cruise range, no movement will be imparted to the pinion gears 156 and the high lead screws 155 or the control ring 151 due to the intermittent drive mechanism.

The cam flange 309 is biased by lever spring assemblies 311 and 312 which resiliently urge the cam flange 309 into the path of movement of the member 307. As seen in Fig. 10, the leaf springs 311 and 312 react against studs 313 and 314, respectively, which pass through apertures in the cam flange 309 and are anchored in the ring gear 136. Thus, the leaf spring assemblies 311 and 312 constantly urge the cam flange 309 into engagement with the outer periphery of the ring gear 136. In addition, a third stud 315 extends through an aperture in the cam flange 309 and is anchored to the ring gear 136. The stud 315 pilots the cam flange 339 on the ring gear 136 and prevents relative angular movement therebetween.

The ring gear 136 is also formed with radially extending lugs 316, 317 and 318, which are circumferentially spaced, as seen in Fig. 10. The solenoid stop member is arranged to engage the radially extending lug 317, when the solenoid 134 is decnergized to limit movement of the ring gear 136 throughout the angular distance between lugs 316 and 317 wherein the pitch position of the blades can be controlled between the flight idle position of +20 and full feather. As aforementioned counterclockwise rotation of the ring gear 136 calls for movement of the blades in the decrease pitch direction, whereas clockwise rotation of the ring gear 136 calls for movement of the blades in the increase pitch direction. The position of ring gear 136, as shown in Fig. 10, is within the cruise range of movement of the power lever 108. When the solenoid stop member 135 is removed, the control ring gear 136 can be rotated in a counterclockwise direction past the stop member 135 within the range between the radially extending lugs 317 and 318, which constitutes the beta range between full reverse and flight idle.

The beta range of power lever movement between full reverse and flight idle is indicated by the arcuate distance between the lines so labeled in Fig. 10 with reference to the edge 319 of the lug 316. Similarly, the arcuate distance equivalent to the non-beta follow-up portion of the cruise range of power lever movement is indicated in Fig. as being equal to the arcuate extent of the cam flange 309. Likewise, the arcuate distance of the cruise range adjacent the take-off line in Fig. 10 corresponds to movement of the power lever in the beta follow-up range. The arcuate distance between-the take-off line and the feather line in Fig. 10 represents the movement imparted to the control ring gear 136 when the emergency lever 107 is pulled.

The novel beta follow-up system, or variable hydraulic low pitch stop, is operative during a portion of the power lever movement in the cruise range, during which movement, the ring gear 136 imparts rotation to the pinion gears 156 and the highlead screws 155 in a clockwise direction so as to move the control ring 151 axially to the right, as viewed in Fig. 9.

.time, no movement is imparted to the control ring 151.

Accordingly, the governor has control over propeller pitch, and if the governor is operating properly as fuel vflow to the turbine is increased, turbine speed will increase and the governor will call for an increase in blade angle in an attempt to maintain turbine speed substantially constant. Thus, during power lever movement within the non-beta follow-up portion of the cruise range, if the governor is operating properly, the propeller blades will be moving in an increase pitch direction from the flight idle angle of However the minimum scheduled blade angle in the cruise range is +20, as seen in Fig. 12.

During power lever movement in the beta follow-up portion of the cruise range to the take-off position, the blade angle is manually scheduled to increase from +20 to to +32, as seen in Fig. 12. The beta follow-up system therefor provides overspeed protection during take-off. In addition, if the turbine driving the engine should fail, or malfunction, during take-off, the pitch position of the blades of that particular propeller will have been increased to +32 so as to appreciably reduce the drag created by a failing turbine. As soon as the aircraft is air-borne and the power lever is returned to the non-beta follow-up portion of the cruise range, the hydraulic low pitch stop position is again reduced to +20.

The hydraulic low pitch stop, which is operative in the governed speed regime, operates in the following manner.

Since, as aforementioned, the feedback mechanism is operative within the range of angles from .7 to +32, when the control ring gear 136 is in the non-beta follow-up portion of the cruise range, the end of the lever 287 attached to the shoe 286 has a predetermined position. The position of this lever end is such that when the blades are at +20", the rotary feedback shaft 290 will have positioned the nut 288 so that the follower 289. engages the cam surface 285 of the lever 223. When the follower 289 engages the cam surface 285 of the lever 223, it positions the valve element 209 so thatthe ports 220 are closed by the land 221, thereby cutting on flow to the larger area of the differential piston so that the distributor valve 213 will, in turn, cut off the flow of fluid to the decrease pitch chambers 256 of the torque units. This cut oif of flow to the decrease pitch chambers of the torque unit prevents movement of the blades below the hydraulic low pitch stop position of 20. The mechanical low pitch stop 195 is set to positively prevent movement of the blades below a ,+l8 when the conduit 281 is connected to drain, and,

'range to the take-off position, the control ring 1511s moved axially to the right so as to advance the hydraulic low pitch stop so it will become operative to prevent movement of the blades below a +32 at the take-oil position. i The speed sensitive pitch lock control valve 273 isresponsive to propeller speed and at a predeterminedpropeller overspeed, for instance, 5% above the governor speed setting, the valve 273 will move against its spring 320 so as to connect passage 321 to drain. During normal propeller operation, the passage 321 is connected to the pressure passage 204 so as to maintain the servo valve When the servo valve 272 nected to passage 322, which connects to conduit 323 and the release chamber of the mechanical pitch lock 196. Thus, during normal propeller operation, the pitch lock is disengaged from the master gear 197 so as to permit pitch changing movement in the decrease pitch direction.

The solenoid valve assembly '32 comprises a solenoid valve 330, which is reciprocable in a bore 331 located at' substantially right angles to a radial line from the propeller axis. Thus, centrifugal force has no effect on the position of the solenoid valve. The solenoid valve 330 has ports 332 and 333 connected to conduits 334 and 335, respectively, which are, in turn, connected, respectively, to the increase pitch chambers 241 and the decrease pitch chambers 256 of the torque units, in parallel with the connections from the distributor valve 213. The port 332 communicates with a pressure compensating valve assembly 336 which, per se, constitutes no part of this invention and is of the type disclosed in copending application Serial No. 259,252, now abandoned, filedNovember 30, 1951, in the name of Dale W. Miller, and assigned to the assignee of this invention. The solenoid valve element 330 is spring-centered to a position where lands 337 and 338 block ports 332 and 333, respectively. Energization of the solenoid windings 339 and 340-is controlled by the electrical phase synchronizer. 126,'which is operative to modulate the hydraulic flow to the torque units so as to maintain the blades of the slave turbinepropeller combination in a predetermined phase relationship with the blades of the master turbine-propeller combination.

The feathering valve assembly 31 also includes a feathen'ng control valve element 350, which is disposed for r biased towards the axis of propeller rotation by a spring 356.

As seen particularly in Figs. 9 and 13, the rod 351 pivotally attached thereto by means of a pin 357 a trolley 358 having diverging arms 359 and 360, which carry follower rollers 361 and 362, respectively. schematically, as shown in Figs. 13 through 16, the roller 361 is engageable with a cam 363 having an actuating surface 364'and an actuating surface 365. structurally, as seen in 19 the arm 358 is bifurcated, each furcation carrying a roller 361 cooperating with furcations of the cam 363. The cam 363 is connected by means of a rod 363a with a shoe 365,'which can be moved axially by axial movement of the feathering ring 150. When the feathering ring 150 is moved axially to the left due to counterclockwise rotation of the high lead screws 153, which movement is effected by clockwise rotation of the feathering ring gear 137 by the feathering lever 96, the cam 363 will be moved from the position of Fig. 13 to the position of Fig. 14 whereupon the roller 361 will move up to the actuating surface 365, thereby imparting movement to the feathering control valve 351 against the spring 356. The movement imparted to the valve element 351 is suflicient to interconnect passages 354 and 355, thereby causing the application of pressure fluid to the servo valve 165 so that it moves against its spring 179. When the valve 165 moves against its spring 179, the passage 259 is connected to the drain passage 258 through the annular groove between lands 174 and 175 whereby the decrease pitch chambers of the torque units are connected to drain; the land 176 blocks communication between passages 173 and 180 whereby the supply of high pressure fluid to the governor valve assembly is blocked, or interrupted, so as to disable control by the distributor valve 213 over propeller pitch; and the pressure passage 173 is connected to the passage 249 through the annular groove between lands 176 and 177 so as to apply high pressure fluid directly through the hub passage 250 to the increase pitch chambers 241 of the torque units from the high pressure conduit 170. Thus, the servo valve 165 performs three functions when it is actuated, namely, disables the distributor valve 213 and, hence, the governor from having control over the pitch position of the propeller blades, connects the decrease pitch chambers to drain and connects the increase pitch chambers directly to the high pressure conduit so as to immediately effect movement of the propeller blades towards the feathered position. As aforementioned, the feathering lever 97 can be actuated by either the feathering solenoid 118 or by the link 140 from the negative propeller shaft torque sensing device, as disclosed in Fig. 8.

In the normal position of the feathering ring 151, the cam 363 is in a position where the spring 356 will position the valve 351 so as to connect passage 355 to drain. In this position, control over propeller pitch is assumed by the distributor valve 213, which is controlled by the valve element 209. Since the valve element 209 is used as a speed sensing element during constant speed operation and as a servo positionable element during beta op eration, it is apparent that all necessary propeller functions can be accomplished by a single valve element which controls the distributor valve 213.

As hereinbefore alluded to, the negative propeller shaft torque sensing device may actuate the feathering lever 97 during a landing approach and, thus, call for movement of the propeller blades in an increase pitch direction when the pilot has manually scheduled a blade angle in the negative thrust range. To prevent the occurrence of this phenomenon, the roller 362 is positioned by a cam element 370 having three distinct actuating surfaces 371, 372 and 373. structurally, the cam element 370 is slidably mounted between the furcations of the cam member 363, as shown in Fig. 9. The cam element 370 is attached to a shoe 374, which is connected to move axially with the control ring 151. When the control ring 151 is moved axially to the left, as viewed in Fig. 9, into the beta range, between full reverse and flight idle, the cam 370 assumes the position shown in Fig. 16, wherein the roller 362 engages surface 373. The surface 373 is designed so that irrespective of whether the roller 361 engages surface 364 or surface 365 of cam 363, the feathering control valve 351 will be in a position wherein the passage 355 is connected to drain. This mechanism constitutes a. block-out, or disabling means,

the clockwise direction by energization of solenoid 18 due to closure of a switch, not shown, when the emergency lever 107 is pulled. Clockwise rotation of the control 'ring gear 136 will effect axial movement of the control ring 151 to the right, while clockwise movement of the feathering ring gear 137 will effect axial movement of the feathering ring 150 to the left. Accordingly, the cams 363 and 373 will' move in opposite directions to the position where roller 361 engages actuating surface 365 of cam 363, while roller 362 engages actuating surface 371 of cam 370. Thus, both the control ring 151 and the feathering ring 150 will actuate the feathering control valve 350 to call for propeller feathering. The doubleacting arrangement is incorporated for actuation by the emergency lever 107 to assure propeller feathering by direct mechanical means, i.e. through the link 105, the coordinating control 102, the link 101, the link 100, bellcrank 99, link 98 and the lever 95 in the event that the electrical systemof the aircraft, which is used to energize the feathering solenoid 118, is inoperative. Moreover, as an additional safety feature, movement of the control lever 95 to the feathered position will also impart movement to the lever 287 through the shoe 286 about its pivotal connection with the nut 288 so that the follower 289 will engage the cam surface 285 and mechanically move the valve element 209 upwardly so as to call for movement of the blades towards the feathered position. Thus, if for some reason the feathering control valve 350 does not actuate the servo valve 165, the propeller blades will be moved to the feathered position by fluid flow as controlled by the distributor valve 213, which will be moved downwardly to call for movement of the blades in theincrease pitch direction when the valve element 209 is mechanically cammed upwardly.

The roller 362 of the trolley 358 engages the actuating surface 372 of the cam 370 when the power lever 108 is positioned between the flight idle angle and the take-off position. Thus, when the power lever is in a position between flight idle and take-off, the feathering cam 363 will be operative to actuate the feathering control valve 350 so as to disable the governor and apply pressure fluid to the torque units to move the propeller blades in an increase pitch direction towards feather. As alluded to hereinbefore, during flight of the aircraft, the negative torque sensing device for actuating the feathering lever 96, does not commit the propeller to feather but only calls for. movement of the blades in an increase pitch direction to reduce the drag, while allowing control of propeller pitch to be restored to the governor if the turbine driving the propeller should recover. On the other hand, whenever the feathering solenoid 118 is energized, the propeller is committed to move to the full feathered position.

With reference to Fig. 9, the feathering pump reservoir is shown connected by a hub passage 380 with the regulator reservoir. The passage 380 connects with the return tube 81 having an open end at the centerline of the feathering reservoir 55 so as to maintain the feathering reservoir full of hydraulic fluid at all times. As aforementioned, the hydraulic fluid in the reservoir is maintained under a slight pressure, 20 p.s.i., since it only receives flow from the drain hub passage 244 through the check valve 245, which is set to open at 20 p.s.i. The check valve 245 is housed within the check valve assembly 71, which is mounted on the back plate 57, as

shown in Fig. 7. 

